Characterization of the Interfaces between IV-IV Semiconductors and Ultra-Thin Oxide films

我们采用椭圆偏振光谱和光电子能谱相结合的方法，研究了氧化膜与碳化硅之间的界面、氧化膜形成后不同热处理对界面结构的影响及其与电学性能的关系，以寻求适合于碳化硅MOSFET的氧化工艺。我们研制了原位椭圆偏振光谱系统，以获得了解碳化硅上超薄氧化膜的形成过程和界面微观结构的知识。结果表明，在氧化初期形成的氧化膜成分不同于化学计量比的SiO_2，界面层的折射率大于SiO_2和SiO_2的折射率，随着热处理的进行而降低。为了弄清界面折射率与界面态密度之间的关系，我们进行了椭圆偏振光谱…对辐照后界面态密度增加的碳化硅MOS结构进行了More和C-V测量。我们发现界面层的折射率随着伽马射线的辐照而增加，这表明椭圆偏振光谱测量得到的折射率与界面态密度密切相关，界面态密度影响了SiCMOSFET的沟道迁移率。用角度分辨X射线光电子能谱和紫外光电子能谱研究了热处理后氧化物/碳化硅界面成分和结合状态的变化。此外，我们还利用显微红外反射光谱对碳化硅大块晶体的电学性质进行了表征，证明了在没有电接触的情况下，可以无损地测量碳化硅晶片中的职业浓度和迁移率的分布。这一研究项目对氧化物/碳化硅界面的结构有了更好的理解，揭示了椭圆偏振光谱是一种很好的表征技术，适用于器件过程中的监测工具。较少

We have used spectroscopic ellipsometry, together with photoelectron spectroscopy, to investigate the interfaces between the oxide film and SiC, structural changes in the interfaces by various kinds of heat treatment after the oxide film formation, and the correlation with their electrical properties, in order to search appropriate oxidation process good for SiC MOSFETs.We have developed in-situ spectroscopic ellipsometry system to acquire the knowledge for clarifying the formation process of ultra-thin oxide films on SiC and microstructure of the interfaces. It is found that the composition of the oxide film formed in the initial stage of oxidization is different from that of stoichiometric SiO_2 and that the refractive indices of the interface layers, which are larger than that of SiC and SiO_2, decrease with heat treatment. In order to make clear the relation between the refractive indices of the interfaces and interface state density, we have carried out spectroscopic ellipsometry … More and C-V measurements for the SiC MOS structures whose interface state density is increased by gamma ray irradiation. We have found that the refractive indices of the interface layers increase with gamma ray irradiation, which suggest that the refractive indices obtained by spectroscopic ellipsometry are closely related to the interface state density, which affects the channel mobility in SiC MOSFET. Angle-resolved x-rays photoemission spectroscopy and ultraviolet photoemission spectroscopy were performed to clarify the change of composition and bonding state at the oxide/SiC interfaces by heat treatment. In addition, we have used micro infrared reflection spectroscopy to characterize the electrical properties of SiC bulk crystals and demonstrated that the distribution of the career concentration and mobility in SiC wafers can be 〓〓〓〓sured nondestructively without electric contacts.This research project brings about a better understanding of the structures of oxide/SiC interfaces and reveals that spectroscopic ellipsometry is an excellent characterization technique and is applicable to monitoring tool during device processes. Less